EP0403685B1 - Process to produce a pipe section of an expandable shaft - Google Patents

Abstract

A process to produce a pipe section of an expandable shaft is described. An inner jacket, an outer jacket and, between them, a middle layer are applied one on top of the other in sandwich design to an inner mould corresponding to the inside diameter of the pipe section, with mould pieces corresponding to openings (15) in the pipe section attached to the inner mould. The inner jacket and the outer jacket consist of synthetic resin-impregnated fibres (1, 2, 4, 5, 10) and the middle layer consists of a honeycomb material. The pipe section is distinguished in particular by light weight and the associated further advantages, in particular with respect to its ease of handling. In order that the necessary openings (15) do not weaken the structure of the carbon fibres (10), the latter are laid around the mould pieces producing the openings (15) and the sandwich structure is subsequently impregnated with the synthetic resin. <IMAGE>

Description

The invention relates to a method for producing a perforated tubular body of an expansion shaft.

Expansion shafts can change their diameter in a controlled manner so that sleeves on which the webs are wound can be rotatably supported and, if necessary, driven using the expansion shafts. So that the expansion shafts can change their diameter, they are provided with openings, through which clamping bodies can pass in the radial direction of the shaft, which bring about the necessary change in the outer diameter of the expansion shaft. An example of such expansion waves is described in US Pat. No. 4,773,656 or in the parallel German utility model 86 34 752.

The tubular bodies of conventional expansion shafts are made of steel or aluminum. A steel tube is machined accordingly to produce the openings in the tube body. This is very labor intensive. In addition, such a tubular body has a considerable weight due to the metal used.

The prior art already includes processes for the production of tubular bodies in lightweight construction, the tubular bodies in sandwich construction having a layer of honeycomb material against which an inner jacket and an outer jacket, each made of synthetic resin-impregnated fibers, bear. See US Pat. No. 4,563,321 or also DE-U-87 08 474. However, tubular bodies of expansion shafts provided with openings are not intended to be produced using the above-described methods.

US-A-3,765,980 describes a method for producing a tubular body provided with a plurality of nozzle openings, wherein pins are inserted into openings of a tubular base body in order to place the fibers of an outer jacket in such a way that the pins remain free. The fibers are then soaked in synthetic resin. After the pins have been pulled out and the synthetic resin material has hardened, a light-weight tubular body is formed with a large number of openings provided over its circumference and length, which serve as nozzles. A tubular body in sandwich construction, as explained above, is not produced by this method.

The invention is therefore based on the object of proposing a method with which a breakthrough tubular body of an expansion shaft can be produced, which is characterized by a noticeably reduced weight, without its mechanical properties suffering.

To achieve this object, the invention is characterized in that an inner jacket, an outer jacket and a middle layer are applied one above the other on an inner shape corresponding to the inside diameter of the tubular body with fittings attached to the inner shape corresponding to the breakthrough of the tubular body, optionally thereon constructing a further middle layer and a further outer jacket, the inner jacket and the outer jacket being made of fibers and the middle layer being applied from a honeycomb material, and the fibers being laid around the shaped pieces without severing them, whereupon the structure is impregnated with synthetic resin, which then cures, using a non-woven fabric, fiber fabric or fiber fabric as the inner jacket, on the outside thereof Fiber cable is applied and a fiber fabric is used as the outer jacket, to which a fiber cable is applied and in turn a fiber ribbon (6), and wherein the inner jacket and / or the outer jacket have fibers (10) which essentially extend in the axial direction ( 9) extend the tubular body.

This leaves the teaching of the prior art, according to which such tubular bodies must in principle be produced from suitable metal (solid material) and, according to the invention, the tubular body is basically manufactured in a sandwich construction from lightweight honeycomb material in a middle layer, which is covered on both sides by carbon fiber layers. The entire structure is then impregnated with synthetic resin, so that a completely stable structure is obtained after the synthetic resin has cured. Tests have shown that a tubular body produced by the method according to the invention weighs only about one tenth of a tubular body according to the prior art, and indeed with the same mechanical properties, in particular the same bending strength.

It is important for the desired high bending load of the tubular body produced by the method according to the invention that the fibers run at least partially and essentially in the axial direction of the tubular body. They absorb the bending stresses. In order not to weaken the bond between the fibers, an important inventive feature provides that the fibers be placed around the shaped pieces which give the openings, without cutting them. As a result, the fibers, in spite of the shaped pieces provided for the breakthroughs, can perform their task of absorbing the loads occurring during operation practically unimpeded take over because they have to be moved only slightly and locally compared to the undisturbed state. Of course, it does no harm if a few of the fibers are cut through, for example unintentionally, as long as the tubular body continues to withstand the stresses placed on it during operation.

The advantages associated with such a lightweight tubular body or with the appropriately completed expansion shaft are obvious. For example, only correspondingly smaller masses need to be stored, accelerated and braked.

A honeycomb structure made of paper material or plastic will be used for the honeycomb material. The synthetic resin inseparably connects the sandwich structure to a one-piece tube.

The inner jacket and the outer jacket made of synthetic resin-soaked fiber fabric will be built up according to the requirements.

The fiber fabric of the inner jacket ensures a smooth surface during the manufacture of the tube, so that it can be easily removed from a base tube on which the tube according to the invention is produced, if necessary with the aid of a suitable release agent. In addition, the fiber fabric provides the necessary basic structure for the fiber cables attached to it. A carbon fiber cable is understood in the sense of the invention to mean a large number of fibers extending in the axial direction of the tube. Above all, these ensure the high bending stiffness of the pipe.

The fiber fabric of the outer jacket covers the honeycomb material and ensures that no liquid synthetic resin gets into the honeycomb penetrates. It also provides the necessary structure for the layer of fiber cables located above it, which here also extends essentially in the longitudinal direction (axial direction) of the tube and which contribute significantly to the desired high bending stiffness of the tube. The structure is closed to the outside by a sliver, which gives the necessary smooth outer surface of the tube.

The statements made above regarding the inner jacket also apply to the structure of the outer jacket, ie the fiber fabric is preferably designed in the manner of a stocking with strands of fibers intersecting at an acute angle. The fiber cable essentially consists of a multiplicity of fibers which extend in the axial direction and are arranged around the tube and are essentially parallel to one another and only slightly twisted together. Finally, the sliver also consists of fibers which extend essentially in the axial direction, but which are connected to one another by transverse threads to form a flat, easy-to-handle band. The sliver does not have to extend in the axial direction, but can also be wound spirally, for example.

Generally it should be explained that the structure of the inner jacket and / or the outer jacket does not have to consist of pure carbon fibers. Carbon fibers or aramid fibers should predominate. Other fibers can be added, for example glass fibers.

• Fig. 1 - zeigt schematisch in einer Stirnansicht einen erfindungsgemäßen Rohrkörper, wobei zur Verdeutlichung der Aufbau des Rohrkörpers in der Einzelheit X vergrößert herausgezeichnet ist;
• Fig. 2 - 5 zeigen in vergrößertem Maßstab und in Draufsicht ein Kohlefasergewebe, ein Kohlefaserkabel, ein Kohlefaserband und ein Wabenmaterial in dieser Reihenfolge;
• Fig. 6 - schematisch eine Seitenansicht zur Erläuterung des erfindungsgemäßen Herstellungsverfahrens und
• Fig. 7 - ebenfalls schematisch eine Draufsicht auf einen Ausschnitt von Fig. 6 in Richtung des Pfeiles A.

The invention is explained in more detail below on the basis of an exemplary embodiment from which further important features result. Carbon fiber is used as an example. Instead of or in addition, aramid fibers can also be provided, or fibers made of other materials that meet the necessary requirements, in particular tensile strength.

• Fig. 1 - shows schematically in a front view a tubular body according to the invention, the structure of the tubular body being shown enlarged in detail X for clarity;
• 2-5 show, on an enlarged scale and in plan view, a carbon fiber fabric, a carbon fiber cable, a carbon fiber tape and a honeycomb material in this order;
• Fig. 6 - schematically a side view for explaining the manufacturing method according to the invention and
• Fig. 7 - also schematically a plan view of a section of Fig. 6 in the direction of arrow A.

The tubular body consists of an inner jacket, a middle layer of honeycomb material and an outer jacket. The inner jacket consists of a carbon fiber fabric 1, over which there are carbon fiber cables 2. (See Fig. 1)

The middle layer consists of a honeycomb material 3 made of a suitable paper material, which is optionally lacquered or impregnated with synthetic resin. This is a commercial product.

The outer jacket consists of a carbon fiber fabric 4, which basically corresponds to the carbon fiber fabric. There is a carbon fiber cable 5 corresponding to the carbon fiber cable 2 and the outside of the tube is covered by a carbon fiber tape 6. This preferably runs spirally around the pipe.

The inner jacket consisting of layers 1, 2 is impregnated with synthetic resin and the same applies to the outer jacket, which consists of layers 4, 5, 6.

The middle class need not consist of paper material. Rather, any suitable honeycomb material can be used for them. The walls forming the honeycombs run in the radial direction.

Fig. 2 shows a view of the flat laid carbon fiber fabric 1.4, from which the strands 7.8 of carbon fibers intersecting at an acute angle can also be seen. The axis of the tube according to Fig. 1 is indicated at item 9.

Fig. 3 shows - also laid flat - the carbon fiber cable 2.5, which consists of a plurality of themselves in the axial direction 9 extending, essentially parallel to each other and only slightly twisted together.

Fig. 4 shows the - also laid flat - carbon fiber tape 9, in which the carbon fibers 10 are connected to one another by transverse threads 11 to form a tape.

FIG. 5 shows the honeycomb material 3, which is also laid flat, with longitudinal webs 12, which are connected to one another via transverse webs 13 placed on a gap. In reality, the honeycomb material is formed by wavy bands which extend in the transverse direction and are each glued to one another at the bases of their U-profiles. The double-laid bases form the transverse webs 13 and the legs of the U-profiles form the longitudinal webs 12.

The tubular body described serves as an expansion wave after appropriate completion.

6 and 7 explain in detail the process steps for producing such a tubular body. 6 shows an inner shape 14 (pipe) on which fittings 15 are fastened in accordance with the openings to be made in the pipe body. The fittings consist, for example, of correspondingly bent sheet metal pieces which are glued to the inner mold 14. Other fastening options and types of manufacture for the fittings are also possible. It should also be mentioned that for the sake of simplicity only one of the shaped pieces is shown in FIG. 6, in reality there are several of these shaped pieces, possibly also with different dimensions and / or profiles.

Rings 16, which complete the shape, are pushed onto the ends of the inner shape 14

Subsequently, the sandwich structure 17 explained above with reference to FIGS. 1 to 5 is applied over the inner mold, the carbon fibers 7, 8, 10 not being cut through in the area of the shaped pieces 15, but instead being put around the shaped pieces 15 in question according to the invention without cutting through them . See Fig. 7.

The sandwich structure is then impregnated with synthetic resin, and after the synthetic resin has hardened, the shaped pieces 15 are removed and the finished tubular body with its openings corresponding to the shaped pieces 15 can be pulled off the inner mold 14. It can then be completed into an expansion shaft or a winding shaft.

The openings in the honeycomb material 3 corresponding to the shaped pieces 15 were previously separated from the honeycomb material, for example by appropriate punching or with the aid of a knife.

Claims (4)

1. A process for the manufacture of a tubular body of an expansion shaft said tubular body having apertures therein, characterized in that on an inner form (14) according to the inside diameter of the tubular body provided with form pieces (15) mounted at the inner form according to the apertures of the tubular body, an inner coat (1, 2), an outer coat (4, 5, 6) and between these a central layer (3) are applied superposed in sandwich construction, possibly constructing upon this a further central layer and a further outer coat, wherein the inner coat and the outer coat are laid of fibers and the central layer is applied of a honeycomb material, and wherein the fibers (10) are placed around the form pieces (15) without seperating the fibers, whereupon the construction is saturated with artificial resin which subsequently is hardening, wherein as inner coat a fiber vleece, a fiber nest or a fiber texture (1) is used, on the outside of which a fiber cable (2) is applied, and as an outer coat a fiber texture (4) is used onto which a fiber cable (5) is applied and onto same again a fiber band (6), and wherein the inner coat and/or the outer coat are provided with fibers (10) extending substantially in axial direction (9) of the tubular body.
2. A process according to claim 1, characterized in that for the passage of the form pieces (15) pieces are separated from the honeycomb material.
3. A process according to claims 1 or 2, characterized in that for the honeycomb material (3) a paper material or a plastic material is used.
4. A process according to any of claims 1 to 3, characterized in that as components of the inner coat (1, 2) and/or of the outer coat (4, 5, 6) at least mostly carbon fibers and/or aramide fibers are used.

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